Ignition control device and method

ABSTRACT

An ignition control device for controlling an ignition coil device for an internal combustion engine, having an angle measuring device for measuring the current crank angle of the internal combustion engine and for outputting an equidistant angle pulse signal and an angle signal for indicating the respective beginning of a working cycle. The ignition control device includes a synchronization device for synchronizing the angular positions of the individual cylinders to the output signal of the angle measuring device, a rotational speed measuring device for measuring the rotational speed of the internal combustion engine at a measuring time point within the ignition cycle of an individual cylinder, and a calculating device for calculating a preestablished ignition angle corresponding to the measured rotational speed. A preestablished charging time corresponds to the measured battery voltage, and a beginning charging angle corresponds to the respective calculation angles in accordance with the synchronization. An ignition control value output device for outputting the beginning and the ending of the charging time.

FIELD OF THE INVENTION

The present invention relates to an ignition control device as well asto a corresponding ignition control method.

Although it is applicable to any ignition control system, the presentinvention is discussed with respect to an engine control unit that islocated on board a motor vehicle.

BACKGROUND INFORMATION

Ignition control devices for controlling ignition events for coilignition systems and devices have essentially two control functions:controlling a desired ignition power over the duration of connection,i.e., the duration of the charging of the ignition coil; and controllingan ignition pulse over the duration of disconnection, i.e., thetermination of charging of the coil, using a correct angle.

The ignition power, which in coil ignition systems is metered over acharging time of the coil, is of varying magnitude in accordance withthe vehicle system voltage applied to the electrical circuit of the coiland with the time constant of the electrical circuit.

Usually, the specific setpoint values are stored in the control unit asa characteristics field, as a function of the rotational speed and otherpossible engine parameters.

Conventional ignition control methods are designed for a specificcontrol unit for a specific engine or a specific automobilemanufacturer.

If an ignition control device is to be designed for a control unitplatform that can be used in any SI engine in accordance with thecontrol and regulation requirements of any customer, then new demandsarise for the ignition control method in question.

Conventional ignition output has a substantially self-sufficientoperation. An attempt is made to process as much information as possiblein the ignition output in parallel and independently, so as to obtainthe greatest possible degree of dynamic impact and output precision. Forexample, a separate rotational speed measurement for the ignition outputis customary, being as close as possible, in terms of the angle, to theignition event, in order to keep the error in the necessary predictionof the rotational angle curve in the dynamic as small as possible. Inaddition, an attempt is made to calculate the ignition eventsindividually for each cylinder, to the greatest extent possible inparallel fashion.

For example, if it is detected that, due to the advances in the ignitionevents, the measuring location of the angular velocity must also beshifted, then this shift must be carried out only once and does not havean effect on the calculation of the ignition events for the othercylinders. If an engine control system cannot calculate all of thecylinders individually, for example due to lack of resources, then theattempt is made to form at least one group of cylinders that are similarwithin the engine.

For an ignition system that is designed for a platform, this method isvery expensive, especially in terms of hardware resources. Ignitioncontrol systems that require reduced computing expense show that dynamicerrors can be sufficiently compensated for by dynamic derivative actionswith regard to the ignition angle or the dwell time.

Ignition methods having their own calculation chains avoid applicationexpense, but use more hardware resources, and they also require,depending on the computing architecture, longer job execution times. Afurther point which characterizes many of the ignition outputs usedtoday is that their output signals are usually fixedly assigned tospecific hardware outputs. A method of this type makes projectconfiguration cumbersome when the method is used in a control platform.

Furthermore, a very few ignition output methods check the mixture stateof the cylinder that is to be fired. In the new generations of engines,which use plastic intake pipes, the problem of induction pipe explosionshas arisen in various ways. This problem can be minimized by firstigniting cylinders that are filled in a defined manner.

Therefore, an ignition method has heretofore been lacking that canservice as many cylinders as possible using minimal hardware/controllerresources, that can easily be configured in accordance with targethardware, and that can be controlled by the injection system.

For outputting angle signals, conventional control units use an angletransmitter wheel, which delivers to the ignition control device pulsesthat are equidistant in terms of angle. However, for reasons ofcomputational job execution times, the calculation of the ignitionevents can only take place in most ignition control device architecturesin segments, one segment being the angular interval of 720° of thecrankshaft divided by the number of cylinders, i.e., in a four-cylinderengine, for example, 180°. Therefore, although the angular positions ofthe ignition events ascertained in the calculation are measuredsufficiently precisely via the angle transmitter wheel and thetimer/counter circuits that are customary in the ignition controldevices, nevertheless the calculation itself proceeds on the basis of ameasured rotational speed, which in a rotational speed dynamic is nolonger present at the location of ignition.

SUMMARY OF THE INVENTION

Thus, it is desirable to design an ignition control device for theoutput of ignition events that is able to operate in overall enginecontrol system, which can be used in the greatest possible number ofsystem environments and under the most varied possible systemconditions.

Because only a limited framework for control components is available atany one time (e.g., interrupt channels on a predefined controller) forreasons of cost optimization, the device and the method should be ableto be realized at a minimal expense, above all with respect to hardwareresources. The design of the ignition control method should be modularto the greatest extent possible in order to be able to adjust theignition control method to various control variants as simply aspossible.

The ignition control device according to the present invention has theadvantage, with respect to the conventional approaches to the problem,that the design of the ignition control method incorporates the resultsof analysis of a multiplicity of engine variants. In comparison to thecurrent ignition control methods, the designed ignition output issimpler, more capable of being configured, requires fewer resources, andhas clearly defined interfaces, through which the other engine controlfunctions can interact with the ignition output. In particular, thepotential interaction with the injection output makes it possible toaddress the problem of induction pipe backfiring at 0 rotational speedand the problem of uneven starting.

In contrast to the technically current ignition output methods, thedescribed ignition output interacts with other devices for the output ofhardware events. In this case, one especially favorable interaction is,for example, querying the status of the injection. In this context, theinjection system supplies to the ignition output the information that adefined filling of a cylinder with fuel has taken place. Subsequently,the ignition system will fire this cylinder as a first ignition.

Current ignition outputs begin with the ignition irrespective of themixture state when the beginning of a 360 degree interval is detected orwhen simultaneous cylinder detection occurs. In this context, theignition takes place in undefined mixture states. For example, if atoo-lean mixture is ignited, this can result in delayed combustions andin the worst case, even in an explosion of the induction pipe.Furthermore, given a rich mixture, it is possible for the engine torun-up unevenly as a result of pronounced buildup of film on the wallsin the induction pipe, which has a disturbing effect on the drivingsensitivity, but also potentially on the introduction of exhaust gasreactions.

Conventional technical ignition output methods are not designed with aview to outputting different output patterns simultaneously. Usually,information as to which hardware channels are to be activated in anignition is fixedly bound to the hardware itself. The ignition outputaccording to the present invention is designed to operate in a pluralityof control unit variants with out hardware adjustments and the costsassociated therewith. The form and design of the signals delivered fromthe ignition output to the components can be taken from a table, whichis accessed during the program running time of the calculating routines.Therefore, project adjustments of the software are similarly minimized.

In contrast to conventional systems, in the ignition output described,no autonomous evaluation of the transmitter signal is required. Theevent calculation takes place with regard to the synchronous processthat is generally continually present in engine control systems. As aresult of the fact that the ignition output also makes use of a generalcomparator circuit of the rotational speed measuring device, which canbe configured on the basis of a comparison of time but also of angle,for angle counting and increment refinement only one single activationline is needed for the calculating unit. If the ignition output isconverted to conventional controllers without parallel computing units(so-called economical system), then for the entire ignition output onlytwo interrupt channels are required. If one interrupt is used forsending the current and one interrupt is used for interrupting thecurrent, then any number of cylinders can be served. The assignments ofthe cylinders and their special modes are realized using correspondinglycomplex buffer structures. In this manner, controller and hardwareresources are saved which can be used by other functionalities. Althoughthe ignition output, built up in this manner, has the characteristic ofbeing dynamically somewhat less current than most conventional methods,nevertheless in trials it has been demonstrated that the outputprecision achieved is sufficient for the requirements of an SI engine.

According to one refinement, an enabling device is provided for enablingthe ignition control value output if an injection has occurred.

According to a further refinement, the ignition control value outputdevice is configured such that it outputs the charging time of theignition coil device starting from the beginning charging angle byappending on to the charging time in a charging time output mode, and bycounting out a charging angle until the occurrence of the ignitionevent, in an ignition angle output mode.

According to a further refinement, a table device is provided whichcontains the information that when an ignition event occurs is conveyedto the ignition control value output device.

According to a further refinement, only one single angle/time comparatoris used for calculating the beginning charging angle and the ignitionangle. This implies that there are only two interrupts, i.e., one forthe charging and one for the ignition, irrespective of the number ofcylinders in the internal combustion engine.

According to a further refinement, the calculation of the beginningcharging angle and the ignition angle generally takes place in asynchronous raster, without a special ignition interrupt.

The latter two refinements create an extremely advantageous timingbehavior with regard to the outside.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the basic sequence of synchronization and ignition outputin the ignition control device according to an embodiment of the presentinvention.

FIG. 2 depicts a segment of the basic sequence of synchronization andignition output in the ignition control device according to anembodiment of the present invention, particularly illustrating a forcedignition.

FIG. 3 depicts a schematic representation of a pulse of an angletransmitter wheel.

FIG. 4 depicts a segment of the basic sequence of synchronization andignition output in the ignition control device according to anembodiment of the present invention, particularly illustrating atime/angle relation prediction.

FIG. 5 depicts a schematic representation of the ignition sequence in afour-cylinder internal combustion engine.

FIG. 6 depicts a schematic representation of the ignition controlfunction sequences in the segment of the first cylinder of thefour-cylinder internal combustion engine according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

For explaining the principle underlying the present invention, FIG. 5depicts a schematic representation of the firing order in afour-cylinder internal combustion engine.

In FIG. 5, crank angle KW is entered on the x-axis in degrees and firingsequence ZZ is entered on the y-axis, the firing sequence having theorder . . . 2-1-3-4-2- . . . . A complete cycle amounts to 720° KWcorresponding to a cycle time t_(ZYK). One segment amounts to 720°KW/4=180°, corresponding to a segment time t_(SEG).

FIG. 6 depicts a schematic representation of the ignition controlfunction sequences in the segment of the first cylinder of thefour-cylinder internal combustion engine, with respect to the drive ofignition coil current I_(Z).

At 0°, rotational speed N is measured, and immediately thereaftercharging time t_(L) as well as ignition angle w_(Z) (approximately equalto the final dwell angle) are taken from a characteristics field B.

Thereupon, the beginning dwell and charging angle W_(LB) are determinedfrom the equation

 w _(LB) =w _(Z) −t _(L)·ω

assuming a uniform motion, ω being the angular velocity corresponding torotational speed N. For reasons of computational running time, thetemporal and angular position of the ignition events is only calculatedonce for every firing interval.

In the case of a charging-time output mode, using a counter C1 beginningfrom 0°, angle w_(LB) is measured by crankshaft sensor signal KWS andwhen angle w_(LB) is reached, the end stage of the ignition coil isdriven. Then, charging time duration t_(L) is controlled using a timerand, after charging time duration t_(L) elapses, the driving isinterrupted.

In the case of an ignition-angle output mode, using a counter C1beginning from 0°, angle w_(LB) is measured by crankshaft sensor signalKWS, and the end stage of the ignition coil is driven when angel w_(LB)is reached. Using a further counter C2 beginning from 0°, angle w_(Z) ismeasured by crankshaft sensor signal KWS and, when angle w_(Z) isreached, the driving is interrupted.

Since the faulty calculation of the rotational speed curve, e.g., in theevent of the engine starting, is not negligible, in the ignition controldevices a prioritization is usually undertaken of the control goals,charging time and ignition angle. If the decision is made in favor of aprecise output of the charging time—so-called charging time outputmode—using the timer/counter circuit, then, in the start acceleration(rotational speed increase), a delay shift of the ignition angleresults. On the other hand, if the ignition angle is outputprecisely—so-called ignition angle output mode—, then, in the startingdynamic, the charging time, and therefore the power in the ignitioncoil, is reduced, for which reason misfiring can result.

Therefore, it is advantageous to fixedly prescribe the output method,i.e., charging time output or ignition angle output, as a function ofthe characteristics of the target system, or a switchover in the outputmethod occurs at a threshold rotational speed. In this context, acharging time output is advantageous during the start followed by aswitchover to the ignition angle output beginning at a rotational speedthreshold, at which the rotational speed scanning is at such a highfrequency that the dynamic error is negligible, but at which thesensitivity of the torque sharply decreases over the ignition angle.

FIG. 1 depicts the basic sequence of synchronization and ignition outputin the ignition control device according to an embodiment of the presentinvention.

The specific embodiment depicted relates especially to an ignitioncontrol device for outputting ignition events for SI engines having arotational angle measuring device, i.e., an angle measuring device. Thisrotational angle measuring device primarily delivers to the ignitionoutput pulses at equidistant angles as well as at the beginning of aworking cycle (720° KW in a four-cylinder engine) and at the beginningof a specific segment (180° KW in a four-cylinder engine).

The rotational angle measuring device activates the computing units ofthe output devices once for each firing interval with respect to aspecific rotational angle, the so-called basic value. In the activation,the output devices are delivered information concerning theinstantaneous angular velocity, as well as the number of the cylinder,determined by a synchronization, which is just moving directly to TDC(top dead center of the cylinder to be fired).

In the event that the equidistant angle pulses have a gap, for examplefor reasons of synchronization, the ignition output is supplied theposition of the gap. The ignition output thereupon incorporates the gapinformation into that of the reorganized angular position of the outputevents.

The rotational angle measuring device for the basic value supplies areference time and the number of the angle pulse. The rotational anglemeasuring device counts the angle pulses and at the same time hasavailable to it a free running clock (clock pulse), whose time valuesfor each angle pulse are stored in memory. Using a comparator unit,angle pulse numbers and clock times can be compared. If the comparativeangle state or comparative clock time is equal to the state of the pulsecounter value or the clock time, then the comparator unit triggers acalculation of the ignition output.

If the cylinder assignment and the beginning of the rotational intervalare determined, then the ignition output is periodically activated in aconstant angle interval by the rotational angle measuring device. Theangle interval is derived from the rotational angle for a completeworking cycle of the engine divided by the total number of cylinders.This angle interval is hereinafter termed the firing interval orsegment. The ignition output, in this context, also receives the angularposition of the software reference mark, hereinafter termed the basicvalue. The basic value should ideally be indicated in degrees in frontof the OT of the working cylinder. In what follows, the basic value istherefore regarded as the angular position of the software referencemark with respect to OT.

As is depicted in FIG. 1, in step S100, a synchronization SY of theignition control and the crank angle curve is carried out on the basisof the pulse pattern of the rotational angle measuring device. In stepS200, a cylinder assignment ZZ of the cylinder moving to OT is made. Therotational angle measuring device supplies to the ignition output theinformation that a cylinder assignment has taken place. This means thatthe beginning of a 360° rotational angle interval and the number of thecylinder, which at the beginning of the interval was in the compressionphase, were found. Only when this information has been conveyed does thesynchronization part of the ignition output begin in further checks.

The ignition is only then enabled at step S400 (ZF) when an unambiguouscylinder detection has occurred and the cylinder of the currentsynchronization has been filled to a defined level, i.e., INJ=OK isconfirmed at step S300. So that a defined start-up of the engine cantake place and any delayed combustions can be prevented, the ignitionoutput delays the beginning of further calculations until the device forthe output of injection signals has signaled to the ignition output adefined injection. If an ignition were initiated given undefined mixtureconditions, the engine would be able to start-up in the short-term usinga possible residual wall film and, subsequently, when the wall film wereremoved, would break into the rotational speed before a defined run-uptook place. In addition to the defined start-up, the probability ofinduction pipe backfires is reduced as a result of the enabling of theignition in response to a successful injection. If the ignition has beenenabled, then the ignition remains active for the remainder of thedriving cycle as long as the rotational angle measuring device does notestablish a loss in synchronization between the rotational angle signaland the signal processing methods.

As is depicted in steps S500, S600, and S700, ignition range Z1 isactive at a threshold rotational speed N0, which can be fixedly set.Here, a precise maintenance of the dwell time is guaranteed by theignition output, i.e., the charging time output mode. Above thresholdrotational speed N0, ignition range Z2 is activated, and the preciseignition angle output is guaranteed, i.e., the ignition angle outputmode.

FIG. 2 depicts a segment from the basic sequence of synchronization andignition output in the ignition control device according to anembodiment of the present invention, particularly illustrating a forcedignition.

In accordance with the mechanisms described, the rotational anglemeasuring device activates the ignition output for every cylinder in thecompression phase. In response to activating the ignition output, thecylinder position is before OT by the angle of the basic value. Withinthe firing interval, an ignition pulse must be output before the nextcall of the ignition output. If the preceding ignition has not yet beentriggered during the next call for the ignition output, then theignition pulse is late. In response to errors and to prevent damage tothe ignition components, a forced ignition is then introduced.

In particular, at step S1000, the ignition enabling is checked. If it isthen established at step S1100 that the ignition signal was not yettransmitted by preceding segment ZLS, then at step S1200 forced ignitionZWZ takes place.

For example, if, as a result of an error, for example, an EMVirradiation, faulty behavior of the ignition output occurs leading tolate ignition angles, then the error is reduced as a result of a renewedcall for the ignition output by the rotational angle measuring devicebecause at the beginning of the ignition output, the determinationdepicted in FIG. 2 is carried out.

The ignition output, as noted, receives the number of the cylinder thatis moving to ignition OT that is transmitted by the rotational anglemeasuring device. From the number of the cylinder, an address numberwithin a table is determined, which contains the information that istransmitted to the output unit of the ignition output when the ignitionevent has occurred. The address number is generated from the cylindernumber, the ignition circuit number, as well as the selected outputmode. The cylinder number is transmitted to the ignition output by therotational angle measuring device. The ignition circuit number isfixedly set in the sequence control of the ignition output, and theoutput mode results from the calculation of the ignition events or istransmitted to the ignition output from other devices of the enginecontrol system. Below is a schematic representation of the form of atable of this type.

TABLE I Ignition Masks in Four-Cylinder Engines Conventional CylinderOutput of Emergency Power Number the Ignition Operation Charging OtherModes 1 address1: address5: address9: address13: mask1 mask5 mask9mask13 2 address2: address6: address10: address14: mask2 mask6 mask10mask14 3 address3: address7: address11: address15: mask3 mask7 mask11mask15 4 address4: address8: address12: address16: mask4 mask8 mask12mask16

In the ignition output, temporal events and angle events must besynchronized with each other. FIG. 3 shows a rough sketch of the timingof one single spark on the basis of the signal of the rotational anglemeasuring device.

It can be seen that in one angle interval after the measurement ofsegment time TSEG, i.e., the time for one firing interval, power beginsto be applied to the ignition system. This angle interval is hereinaftertermed the beginning dwell angle. The power is defined in the ignitionoutput discussed here over a time duration, the so-called dwell time.After the elapsing of the dwell time, the power introduced into thesystem is converted into an ignition spark.

Operative for the ignition output are two setpoint values t_(L), w_(Z),which must be coordinated with each other. The setpoint value dwelltime, or charging time, i.e., the power metering duration, istransmitted to the ignition output (time criterion), and the ignitionoutput receives the setpoint ignition angle (angle criterion). Theignition output must therefore calculate at which angle position, beforethe ignition angle, a beginning must be made to introduce power into theignition system, so that the ignition power is sufficient.

For this purpose, in calculating the ignition events, an angle/timecurve must be predicted. The ignition output discussed here, for themotion curve during one firing interval, assumes a uniform, i.e., notaccelerated, motion. For beginning dwell angle Wb, the result then is:

Wb=Wout˜(szout/tseg)*segment angle

given that:

Wout: setpoint ignition angle with respect to the angle position of theignition event calculation

szout: the setpoint dwell time

tseg: presumptive duration of the current segment (this information istransmitted from the rotational angle measuring device to the ignitionoutput).

As soon as the ignition output has been called and the synchronizationand enabling criteria are valid, the ignition output calculates the timefor one angle increment from the predicted segment time of the anglevalues described as integer values, which are processed as in theignition output, as is illustrated in FIG. 4.

As was already demonstrated, the ignition output has the task ofcontrolling a power metering time, and the end of the metering time isreached at the angle location defined over the ignition angle. Thus, theignition output measures both the angle as well as the time intervalsfor the ignition events of the cylinders of the SI engine.

In all output modes of the ignition output, first the beginning dwellangle described above is measured and, at this point, the signal for thepower metering is output from the power-setting device of the ignitionoutput.

As described, the computing logic is activated at the beginning of afiring interval by a general enabling signal of the rotational anglemeasuring device. The enabling signal at the same time activates all ofthe other computing units of the engine control system which mustinteract with the ignition output. At the beginning of the calculations,the ignition output receives from the rotational angle measuring devicethe most recent rotational speed information, which was determined overa defined measuring angle interval.

The rotational speed information is immediately used by the ignitionoutput to determine, in accordance with the above equation, thebeginning dwell angle from the setpoint values for dwell time andignition angle, which are. transmitted by other computing units. Thebeginning dwell angle is produced as the angle interval of the beginningof the power metering regarding the position of the event calculation.This angle is converted into a number of angle transmitter pulsescorresponding to the beginning dwell angle. The residual angle, whichcannot be measured by the angle pulses, is written into a buffer of theoutput unit of the ignition output. The pulse number is transmitted to aswitching unit of the ignition output, which automatically compares thepulse number with a tooth pulse counter of the angle measuring device.If the tooth pulse counter is equal to the pulse number, then thecomputing unit of the ignition output is once again activated, but thistime by the internal switching unit and not by the rotational anglemeasuring device. In the renewed calculation, the residual angle storedin an internal buffer is related to the time for the previous toothperiods of the angle transmitter. This value is queried in therotational angle measuring device. From the residual angle and theprevious tooth period, a period of time results until the actual anglelocation of the beginning of the dwell period; for this purpose, aspecific angle/time motion form of the engine is assumed. The timeduration is in turn transmitted to the internal comparator circuit. Thecircuit this time is connected via a switch to the free running timer ofthe angle measuring device.

The same mechanism as in the case of the tooth comparison occurs thistime at the level of time. If the timer reaches the time comparisonvalue, then the internal circuit in turn triggers a calculation of theignition output. The latter then accesses the mask table described aboveand transmits the table value appropriate to the operating parameters tothe power-setting unit of the ignition output. The power input into thesystem then takes place.

The assumption of constant angular velocity results in the circumstancethat, if the dwell time is output precisely under the influence ofacceleration in accordance with the beginning dwell angle, the actualignition angle is shifted so as to be late in comparison to the setpointvalue of the ignition angle.

If the dwell time is interrupted precisely at the location of theignition angle, the setpoint dwell time could not be maintained. Inprinciple, there are two output methods for the ignition output, whichare both supported by the ignition output under discussion, the preciseoutput of the dwell time or the precise output of the ignition angle.

The precise output of the dwell time, in what follows, is termedignition range 1, and the precise output of the ignition angle, in whatfollows, is termed ignition range 2.

The greatest dynamic fault is achieved in starting the engine. Here, therotational speed actualization is at its lowest and the acceleration atits highest. Since in this phase the angular position of the combustionpoint of concentration, which ultimately is supposed to be controlled bythe ignition angle, is subjected in any case to a tolerance of greaterthan 20%, and, on the other hand, the power requirements of the ignitionsystem are the greatest, above all, in cold starting, the ignitionoutput operates at lower rotational speeds in ignition range Z1. As aresult, maintaining the setpoint power is assured, assuming that alldevices participating in the power switchover are operating normally.The switchover to ignition range Z2 is parametrized using a constant. Asa result, it is possible to have the ignition output operatingexclusively in one of the two modes.

In ignition range Z2, the ignition angle as well as the beginning dwellangle are driven by the counting-out of angle pulses. The dwell periodis maintained as effectively as the angle/time curve of the engine inthe power calculation was predicted by the rotational angle measuringdevice, when the ignition output was called.

In ignition range Z1, after the beginning dwell angle is reached, thetable value of the power-setting device is transmitted. At the locationof the dwell beginning, the switching unit is switched over to the timercomparison in order to compare the tooth counter and the timer of theangle measuring device, and it is charged using the dwell time as atimer comparison value. In this manner, the dwell period is preciselymaintained by the high-resolution timer of the angle measuring device.Here too, a dynamic fault can result, this time in the position of theignition angle, from the quality of the prediction of the angle/timecurve of the rotational motion.

The ignition events, the power charging and the ignition, are onlydriven by two interrupts, i.e., for the ignition only two lines/channelsare required from a comparator unit of the rotational angle measuringdevice.

The comparator unit, in the event of agreement with an angle pulsevalue, triggers the calculation of the increment refinements and isautomatically switched over to timer comparison, under which theresidual angle is counted out. The comparator unit counts out either thebeginning dwell angle and the ignition angle in parallel, or, after thebeginning dwell angle, the ignition signal is triggered by a timercomparison, i.e., the comparator unit is at first not switched at allinto the angle number mode. Therefore, from the comparator unit there isonly one channel to be provided for the ignition and one channel for thebeginning of the charging.

In the related art, a plurality of channels are customary here fordifferent cylinders.

Although the present invention was described above on the basis ofpreferred exemplary embodiments, it is not limited thereto, but ratherit can be modified in many ways.

In particular, the present invention is not limited to a four-cylinderinternal combustion engine, but can be generalized as desired.

In addition, apart from the injection criterion, other injectionenabling criteria can be built in.

What is claimed is:
 1. A method for operating an internal combustionengine, the internal combustion engine including an ignition outputunit, a crankshaft and an angle transmitter wheel, the method comprisingthe steps of: generating angle pulses at the angle transmitter wheelsynchronously with a motion of the crankshaft; calculating at least onebeginning dwell angle in each segment of an engine cycle of the internalcombustion engine by the ignition output unit, the at least onebeginning dwell angle being determined as a sum of a specific number ofangle pulses and a residual angle; counting the angle pulses;determining whether the specific number of angle pulses has been reachedusing a comparator unit; determining a time for reaching the residualangle including taking into account an instantaneous rotational speed;and after the time for reaching the residual angle has elapsed,triggering a beginning of a charging time of an ignition coil.
 2. Themethod of claim 1, further comprising: calculating by the ignitionoutput unit at least one further quantity for determining an ignitionangle.
 3. The method of claim 1, further comprising: calculating, in asecond mode, an ignition angle as a further quantity, the ignition anglebeing calculated by the ignition output unit as a sum of a number ofangle pulses and a residual angle; after a time for reaching theresidual angle has elapsed, triggering a termination of a charging timeof the ignition coil.
 4. The method of claim 3, further comprising:calculating, in a first mode, a dwell time as a further quantity fordetermining the ignition angle; and triggering a termination of acharging time of the ignition coil after the dwell time elapses usingthe comparator unit.
 5. The method of claim 4, further comprising:switching the ignition output unit alternatingly between the first modeand the second mode as a function of an operating parameter.
 6. Themethod of claim 5, wherein the operating parameter is one of rotationalspeed and a time after a starting of the internal combustion engine. 7.The method of claim 1, further comprising: expressing, using theignition output unit, at least one of the residual angle and the dwelltime as a number of clock pulses of an independent clock-pulse.generator, the independent clock-pulse generator functioningindependently of crankshaft motion, each of the clock pulses beingrelayed to the comparator unit.
 8. The method of claim 4, wherein theignition output unit is coupled to the comparator unit via a first lineand a second line, a first signal generated by the comparator unit atthe beginning of the charging time of the ignition coil being suppliedto the ignition output unit via the first line, and a second signalgenerated by the comparator unit at the termination of the charging timeof the ignition coil being supplied to the ignition output unit via thesecond line.
 9. The method of claim 1, wherein the calculating stepincludes calculating the at least one beginning dwell angle after aninjection.
 10. An apparatus for operating an internal combustion engineincluding a crankshaft, comprising: an angle transmitter wheel thatgenerates angle pulses synchronously with the crankshaft; a comparatorunit that determines whether a specific number of angle pulses has beenreached; and an ignition output unit configured to calculate at leastone beginning dwell angle in each segment of an engine cycle of theinternal combustion engine, the ignition output unit including a firstarrangement configured to determine the at least one beginning dwellangle as a sum of a number of angle pulses and a residual angle, and anactivatable calculating unit, the calculating unit determining a timerequired for the residual angle taking into account an instantaneousrotational speed; wherein the comparator unit determines whether thetime required for the residual angle has elapsed so that a beginning ofa charging time of an ignition coil is triggered.
 11. The apparatus ofclaim 10, wherein the ignition output unit is configured to calculate atleast one further quantity determining an ignition angle.
 12. Theapparatus of claim 10, wherein the ignition unit has a first mode and ina second mode, in the second mode, the ignition unit is configured tocalculate a setpoint ignition angle as a further quantity determining anignition angle, the first arrangement of the ignition output unitconfigured to determine the setpoint ignition angle as a sum of a numberof angle pulses and a residual angle, and after the comparator unitsubsequently determines that the time required for the residual anglehas elapsed, a termination of the charging time of the ignition coil istriggered by the comparator unit.
 13. The apparatus of claim 12, whereinwhen the ignition unit is in the first mode, the ignition is configuredto calculate a dwell time as a further quantity determining the ignitionangle, and after the dwell time has elapsed, the comparator unitconfigured to trigger a termination of the charging time of the ignitioncoil.
 14. The apparatus of claim 13, wherein the ignition coil isconfigured to switch alternatingly between the first and second modes asa function of an operating parameter.
 15. The apparatus of claim 14,wherein the operating parameter is one of a rotational speed or a timeafter a starting of the internal combustion engine.
 16. The apparatus ofclaim 10, further comprising: an independent clock-pulse generatoroperating independently of crankshaft motion; wherein the ignitionoutput unit includes a second arrangement configured to express theresidual angle or a dwell time as a number of clock pulses of theindependent clock-pulse generator, the clock pulses of the clock-pulsegenerator being conveyed to the comparator unit.
 17. The apparatus ofclaim 13, further comprising: a first line coupling the comparator unitand the ignition output unit; and a second line coupling the comparatorunit and the ignition output unit; wherein the comparator unit isconfigured to generate a first signal at the beginning of the chargingtime of the ignition coil, the first signal being provided to theignition output unit via the first line, and wherein the comparator unitis configured to generate a second signal at the termination of thecharging time of the ignition coil, the second signal being provided tothe ignition output unit via the second line.
 18. The apparatus of claim10, wherein the first arrangement of the ignition output unit calculatesthe beginning dwell angle after an injection occurs.